Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1557892 > unrolled thread

[PATCH 5/6] f2fs: add a kernel thread to issue discard commands asynchronously

Back to article view | Back to linux.kernel

This discussion starts older than the indexed window; earlier articles aren't shown. The article labeled Started by below is the oldest one visible, not the original post.

Contents

  [PATCH 5/6] f2fs: add a kernel thread to issue discard commands asynchronously Jaegeuk Kim <jaegeuk@kernel.org> - 2017-01-12 23:50 +0100
    Re: [PATCH 5/6] f2fs: add a kernel thread to issue discard commands  asynchronously Christoph Hellwig <hch@infradead.org> - 2017-01-13 09:10 +0100
      Re: [PATCH 5/6] f2fs: add a kernel thread to issue discard commands  asynchronously Jaegeuk Kim <jaegeuk@kernel.org> - 2017-01-13 20:20 +0100
        Re: [PATCH 5/6] f2fs: add a kernel thread to issue discard commands  asynchronously Christoph Hellwig <hch@infradead.org> - 2017-01-16 18:40 +0100

#1557892 — [PATCH 5/6] f2fs: add a kernel thread to issue discard commands asynchronously

This patch adds a kernel thread to issue discard commands.
It proposes three states, D_PREP, D_SUBMIT, and D_DONE to identify current
bio status.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
---
 fs/f2fs/f2fs.h    |  11 +++++
 fs/f2fs/segment.c | 128 +++++++++++++++++++++++++++++++++++++++++-------------
 2 files changed, 108 insertions(+), 31 deletions(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index e7b403cbd70f..ef5e3709c161 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -129,6 +129,7 @@ enum {
 };
 
 #define MAX_DISCARD_BLOCKS(sbi) (1 << (sbi)->log_blocks_per_seg)
+#define DISCARD_ISSUE_RATE	8
 #define DEF_CP_INTERVAL			60	/* 60 secs */
 #define DEF_IDLE_INTERVAL		5	/* 5 secs */
 
@@ -177,18 +178,28 @@ struct discard_entry {
 	int len;		/* # of consecutive blocks of the discard */
 };
 
+enum {
+	D_PREP,
+	D_SUBMIT,
+	D_DONE,
+};
+
 struct discard_cmd {
 	struct list_head list;		/* command list */
 	struct completion wait;		/* compleation */
 	block_t lstart;			/* logical start address */
 	block_t len;			/* length */
 	struct bio *bio;		/* bio */
+	int state;			/* state */
 };
 
 struct discard_cmd_control {
+	struct task_struct *f2fs_issue_discard;	/* discard thread */
 	struct list_head discard_entry_list;	/* 4KB discard entry list */
 	int nr_discards;			/* # of discards in the list */
 	struct list_head discard_cmd_list;	/* discard cmd list */
+	wait_queue_head_t discard_wait_queue;	/* waiting queue for wake-up */
+	struct mutex cmd_lock;
 	int max_discards;			/* max. discards to be issued */
 };
 
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index e3bec31de961..74364006bfa6 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -628,7 +628,7 @@ static void locate_dirty_segment(struct f2fs_sb_info *sbi, unsigned int segno)
 	mutex_unlock(&dirty_i->seglist_lock);
 }
 
-static struct discard_cmd *__add_discard_cmd(struct f2fs_sb_info *sbi,
+static void __add_discard_cmd(struct f2fs_sb_info *sbi,
 			struct bio *bio, block_t lstart, block_t len)
 {
 	struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
@@ -638,12 +638,30 @@ static struct discard_cmd *__add_discard_cmd(struct f2fs_sb_info *sbi,
 	dc = f2fs_kmem_cache_alloc(discard_cmd_slab, GFP_NOFS);
 	INIT_LIST_HEAD(&dc->list);
 	dc->bio = bio;
+	bio->bi_private = dc;
 	dc->lstart = lstart;
 	dc->len = len;
+	dc->state = D_PREP;
 	init_completion(&dc->wait);
+
+	mutex_lock(&dcc->cmd_lock);
 	list_add_tail(&dc->list, cmd_list);
+	mutex_unlock(&dcc->cmd_lock);
+}
+
+static void __remove_discard_cmd(struct f2fs_sb_info *sbi, struct discard_cmd *dc)
+{
+	int err = dc->bio->bi_error;
 
-	return dc;
+	if (err == -EOPNOTSUPP)
+		err = 0;
+
+	if (err)
+		f2fs_msg(sbi->sb, KERN_INFO,
+				"Issue discard failed, ret: %d", err);
+	bio_put(dc->bio);
+	list_del(&dc->list);
+	kmem_cache_free(discard_cmd_slab, dc);
 }
 
 /* This should be covered by global mutex, &sit_i->sentry_lock */
@@ -653,31 +671,28 @@ void f2fs_wait_discard_bio(struct f2fs_sb_info *sbi, block_t blkaddr)
 	struct list_head *wait_list = &(dcc->discard_cmd_list);
 	struct discard_cmd *dc, *tmp;
 
+	mutex_lock(&dcc->cmd_lock);
 	list_for_each_entry_safe(dc, tmp, wait_list, list) {
-		struct bio *bio = dc->bio;
-		int err;
 
-		if (!completion_done(&dc->wait)) {
-			if ((dc->lstart <= blkaddr &&
-					blkaddr < dc->lstart + dc->len) ||
-					blkaddr == NULL_ADDR)
+		if (blkaddr == NULL_ADDR) {
+			if (dc->state == D_PREP) {
+				dc->state = D_SUBMIT;
+				submit_bio(dc->bio);
+			}
+			wait_for_completion_io(&dc->wait);
+
+			__remove_discard_cmd(sbi, dc);
+			continue;
+		}
+
+		if (dc->lstart <= blkaddr && blkaddr < dc->lstart + dc->len) {
+			if (dc->state == D_SUBMIT)
 				wait_for_completion_io(&dc->wait);
 			else
-				continue;
+				__remove_discard_cmd(sbi, dc);
 		}
-
-		err = bio->bi_error;
-		if (err == -EOPNOTSUPP)
-			err = 0;
-
-		if (err)
-			f2fs_msg(sbi->sb, KERN_INFO,
-				"Issue discard failed, ret: %d", err);
-
-		bio_put(bio);
-		list_del(&dc->list);
-		kmem_cache_free(discard_cmd_slab, dc);
 	}
+	mutex_unlock(&dcc->cmd_lock);
 }
 
 static void f2fs_submit_discard_endio(struct bio *bio)
@@ -685,8 +700,48 @@ static void f2fs_submit_discard_endio(struct bio *bio)
 	struct discard_cmd *dc = (struct discard_cmd *)bio->bi_private;
 
 	complete(&dc->wait);
+	dc->state = D_DONE;
 }
 
+static int issue_discard_thread(void *data)
+{
+	struct f2fs_sb_info *sbi = data;
+	struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
+	wait_queue_head_t *q = &dcc->discard_wait_queue;
+	struct list_head *cmd_list = &dcc->discard_cmd_list;
+	struct discard_cmd *dc, *tmp;
+	struct blk_plug plug;
+	int iter = 0;
+repeat:
+	if (kthread_should_stop())
+		return 0;
+
+	blk_start_plug(&plug);
+
+	mutex_lock(&dcc->cmd_lock);
+	list_for_each_entry_safe(dc, tmp, cmd_list, list) {
+		if (dc->state == D_PREP) {
+			dc->state = D_SUBMIT;
+			submit_bio(dc->bio);
+			if (iter++ > DISCARD_ISSUE_RATE)
+				break;
+		} else if (dc->state == D_DONE) {
+			__remove_discard_cmd(sbi, dc);
+		}
+	}
+	mutex_unlock(&dcc->cmd_lock);
+
+	blk_finish_plug(&plug);
+
+	iter = 0;
+	congestion_wait(BLK_RW_SYNC, HZ/50);
+
+	wait_event_interruptible(*q,
+		kthread_should_stop() || !list_empty(&dcc->discard_cmd_list));
+	goto repeat;
+}
+
+
 /* this function is copied from blkdev_issue_discard from block/blk-lib.c */
 static int __f2fs_issue_discard_async(struct f2fs_sb_info *sbi,
 		struct block_device *bdev, block_t blkstart, block_t blklen)
@@ -707,13 +762,11 @@ static int __f2fs_issue_discard_async(struct f2fs_sb_info *sbi,
 				SECTOR_FROM_BLOCK(blklen),
 				GFP_NOFS, 0, &bio);
 	if (!err && bio) {
-		struct discard_cmd *dc = __add_discard_cmd(sbi, bio,
-						lblkstart, blklen);
-
-		bio->bi_private = dc;
 		bio->bi_end_io = f2fs_submit_discard_endio;
 		bio->bi_opf |= REQ_SYNC;
-		submit_bio(bio);
+
+		__add_discard_cmd(sbi, bio, lblkstart, blklen);
+		wake_up(&SM_I(sbi)->dcc_info->discard_wait_queue);
 	}
 	return err;
 }
@@ -920,14 +973,11 @@ void clear_prefree_segments(struct f2fs_sb_info *sbi, struct cp_control *cpc)
 	struct list_head *head = &(SM_I(sbi)->dcc_info->discard_entry_list);
 	struct discard_entry *entry, *this;
 	struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);
-	struct blk_plug plug;
 	unsigned long *prefree_map = dirty_i->dirty_segmap[PRE];
 	unsigned int start = 0, end = -1;
 	unsigned int secno, start_segno;
 	bool force = (cpc->reason == CP_DISCARD);
 
-	blk_start_plug(&plug);
-
 	mutex_lock(&dirty_i->seglist_lock);
 
 	while (1) {
@@ -980,12 +1030,11 @@ void clear_prefree_segments(struct f2fs_sb_info *sbi, struct cp_control *cpc)
 		SM_I(sbi)->dcc_info->nr_discards -= entry->len;
 		kmem_cache_free(discard_entry_slab, entry);
 	}
-
-	blk_finish_plug(&plug);
 }
 
 int create_discard_cmd_control(struct f2fs_sb_info *sbi)
 {
+	dev_t dev = sbi->sb->s_bdev->bd_dev;
 	struct discard_cmd_control *dcc;
 	int err = 0;
 
@@ -1000,11 +1049,22 @@ int create_discard_cmd_control(struct f2fs_sb_info *sbi)
 
 	INIT_LIST_HEAD(&dcc->discard_entry_list);
 	INIT_LIST_HEAD(&dcc->discard_cmd_list);
+	mutex_init(&dcc->cmd_lock);
 	dcc->nr_discards = 0;
 	dcc->max_discards = 0;
 
+	init_waitqueue_head(&dcc->discard_wait_queue);
 	SM_I(sbi)->dcc_info = dcc;
 init_thread:
+	dcc->f2fs_issue_discard = kthread_run(issue_discard_thread, sbi,
+				"f2fs_discard-%u:%u", MAJOR(dev), MINOR(dev));
+	if (IS_ERR(dcc->f2fs_issue_discard)) {
+		err = PTR_ERR(dcc->f2fs_issue_discard);
+		kfree(dcc);
+		SM_I(sbi)->dcc_info = NULL;
+		return err;
+	}
+
 	return err;
 }
 
@@ -1012,6 +1072,12 @@ void destroy_discard_cmd_control(struct f2fs_sb_info *sbi, bool free)
 {
 	struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
 
+	if (dcc && dcc->f2fs_issue_discard) {
+		struct task_struct *discard_thread = dcc->f2fs_issue_discard;
+
+		dcc->f2fs_issue_discard = NULL;
+		kthread_stop(discard_thread);
+	}
 	if (free) {
 		kfree(dcc);
 		SM_I(sbi)->dcc_info = NULL;
-- 
2.11.0

[toc] | [next] | [standalone]

#1558090 — Re: [PATCH 5/6] f2fs: add a kernel thread to issue discard commands asynchronously

On Thu, Jan 12, 2017 at 02:44:06PM -0800, Jaegeuk Kim wrote:
> This patch adds a kernel thread to issue discard commands.
> It proposes three states, D_PREP, D_SUBMIT, and D_DONE to identify current
> bio status.

Why?  Instead of creating the complexity of a thread you should look
into issuing the discard bios asynchronously, which should help to
simplify a lot of the discard logic in f2fs.

[toc] | [prev] | [next] | [standalone]

#1558693 — Re: [PATCH 5/6] f2fs: add a kernel thread to issue discard commands asynchronously

On 01/13, Christoph Hellwig wrote:
> On Thu, Jan 12, 2017 at 02:44:06PM -0800, Jaegeuk Kim wrote:
> > This patch adds a kernel thread to issue discard commands.
> > It proposes three states, D_PREP, D_SUBMIT, and D_DONE to identify current
> > bio status.
> 
> Why?  Instead of creating the complexity of a thread you should look
> into issuing the discard bios asynchronously, which should help to
> simplify a lot of the discard logic in f2fs.

Previously, I've done to issue discard bios asynchronously. But the problem that
I've got is that was not enough. When testing nvme SSD with noop IO scheduler,
submit_bio() was blocked at every 8 async discard bios, resulting in very slow
checkpoint process which blocks most of other FS operations.

Thanks,

[toc] | [prev] | [next] | [standalone]

#1559937 — Re: [PATCH 5/6] f2fs: add a kernel thread to issue discard commands asynchronously

On Fri, Jan 13, 2017 at 11:12:11AM -0800, Jaegeuk Kim wrote:
> Previously, I've done to issue discard bios asynchronously. But the problem that
> I've got is that was not enough. When testing nvme SSD with noop IO scheduler,
> submit_bio() was blocked at every 8 async discard bios, resulting in very slow
> checkpoint process which blocks most of other FS operations.

Where does it block?  Are you running out of request?  What driver is
this on top of?

[toc] | [prev] | [standalone]

Back to top | Article view | linux.kernel

csiph-web